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Classification and composition of overhead lines

The main components of overhead lines are: wires and lightning conductors (overhead ground wires), towers, insulators, fittings, tower foundations, stay wires and grounding devices, etc.

Classification of overhead lines

1 Overhead power transmission line:
it is responsible for the task of transmitting electric energy from power plants, hub substations or intermediate substations to distant industrial cities or places where agricultural electricity is intensively used. Its voltage level is generally 35-330KV. The distance is generally more than 25Km, and the overhead lines or cable lines used to transmit electric energy are called transmission lines.

2 distribution lines:
Overhead distribution line: It is responsible for supplying power from the substation to nearby power consumption units. Its voltage level is generally 10KV and below, and the transmission radius is about 10Km.

Composition of overhead lines

Overhead cable lines are mainly composed of lightning protection wires, wires, line fittings, insulators, pole towers (including poles and iron towers), guy wires and tower pole foundations. Their uses are as follows:

1. Lightning conductors are used to protect overhead lines from lightning and atmospheric over voltage damage. Generally, overhead lines of 10KV and below are not equipped with lightning conductors.

2. Wire Wire is the main component of the line and is used to transmit current. Generally, a single wire is used for each phase of the line. For ultra-high-voltage large-capacity transmission lines, due to the large transmission capacity and to reduce corona loss and corona interference, split conductors in the same phase are often used, that is, two, three, four or more conductors are used for each phase.

3. Line fittings The metal accessories required to connect insulators and cross arms, insulators and wires, and wires themselves are commonly referred to as line fittings. Commonly used line metals include hoops, wire clamps, pull plates, pad irons, through-bolts, turnbuckle screws and right-angle hanging plates.

4. Insulator The insulator is used to support or hang the wire and insulate the wire from the tower. It should ensure sufficient electrical insulation strength and mechanical strength.

5. The role of tower poles is to support conductors, lightning protection lines and their accessories. Reinforced concrete poles are mostly used for 10KV and below. According to their use, they are divided into straight poles, tension poles, corner poles, terminal poles, branch poles and Special rods, etc.

6. The function of the guy wire and the tower foundation guy wire is to strengthen the strength and stability of the pole and balance the force in all directions of the pole. The tower foundation is a facility to fix the tower underground to ensure that the tower does not tilt and collapse.
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